Testing, simulation and design of built-up cold-formed steel-lightweight concrete (CFS-LWC) composite beams subjected to elevated temperatures

• Fire resistance tests performed on cold-formed steel lightweight concrete (CFS-LWC) composite beams. • Material properties of CFS at elevated temperatures and LWC at room temperature determined. • Design procedures to determine the bending resistance of the CFS-LWC composite beams in fire assessed. • Detailed numerical modelling of fire performance of the CFS-LWC composite beams carried out. • Worked example for the design of CFS-LWC composite beams in fire presented. Cold-formed steel (CFS) products are lightweight, structurally efficient and highly versatile, making them suitable for a wide range of construction applications. Although studies have been performed to analyse the flexural behaviour of CFS composite beams at room temperature, their performance at elevated temperatures has yet to be investigated; this is, therefore, the focus of the present study. Through experiments, the structural fire performance of innovative built-up CFS-lightweight concrete (LWC) composite beams is examined. Two full-scale fire tests on simply-supported CFS-LWC composite beams are presented. The test setup, test procedure and obtained results, including the temperature evolution, fire resistance time and failure modes, are described. A numerical modelling study is also presented through which additional insights into the observed structural behaviour are gained. Comparisons between the experimental results and those determined according to EN 1994–1–2 design provision are presented. The results showed that, despite the studied CFS-LWC composite sections being beyond the scope of the code, good predictions of fire resistance were obtained.